One common form of pleated air filters is known as a panel filter in which a rectangular card of pleated filter medium is secured within a rectangular paper board frame (e.g. such as fiberboard or cardboard). One common use for such panel filters is in HVAC systems for homes and other buildings where heating, ventilation and/or air conditioning is desired. Because such pleated panel filters are typically low cost disposable items, it is highly desirable to produce such pleated air filters using automated machinery and automated processes which allow manufacturing costs of the filter to be minimized.
Additionally, it is known that the porous filter media which is formed into a pleated accordion like structure may be “self supporting” as disclosed, for example, in U.S. Patent Publication No. 2006/0283162 to Dent et al; and U.S. Pat. No. 7,255,723 to Choi et al.; U.S. Pat. No. 7,156,891 to Winters et al.; and U.S. Pat. No. 6,254,653 to Choi et al. the entire disclosures of these four patent publications is hereby incorporated by reference in their entireties. For example, one form of a self supporting pleated filter medium comprises a multi-component filtration fibers including low melt components and high melt components that have higher melting temperature than the low melt component. In these arrangements, the low melt component is partially melted to a glassy or partially liquefied state and serves to bind the high melt fibers together, thus forming a heat set into the pleats of the pleated filter medium. As a consequence, this filter medium known as self-supporting pleated filter medium, tends to be relatively stiff in nature as compared to other filtration mediums that do not include such a stiffening binder component. Self-supporting pleated filter medium may also include other forms of adhesives or the like within the fibers to provide such a relatively stiff character to pleated filter media card so that while in use, the filter medium is sufficiently stiff and self-supporting to maintain the pleated form when subjected to passage of fluid such as a forced air flow of HVAC systems in buildings. An advantage of such self-supporting media is that wire scrims that may be co-pleated to provide the support for such pleated filter medium may be eliminated or at least reduced in structure. The amount of other external supports to the filter medium can be thus reduced.
While self-supporting pleated filter medium has provided an advance in the art, it is not without its drawbacks in that the relatively stiff nature can pose difficulties. The present invention is directed towards improvements that are particularly advantageous to such self-supporting pleated panel filter elements and can be applied to those embodiments such as described in the above incorporated by reference patent publications or to other such self-supporting applications, and even potentially to other non self-supporting pleated filter element applications.